Case 1 : Common edible salt, NaCl Sodium Chloride ) obtained from seawater or from lakes contains many impurities such as sulphates of sodium and magnesium along with chlorides of calcium and magnesium. The chlorides of these metals are particularly undesirable being deliquescent in nature. A saturated solution of salt in a minimum quantity of water is prepared and insoluble impurities are filtered off. HCL gas is then passed through the saturated solution and the crystals of pure NaCl separate out. the soluble impurities remain in the solution. Pure crystals of NaCl are filtered, washed and dried.
Which of the following compound is alkaline in an aqueous medium?

Options

A. Na2CO3
B. NaCl
C. H2CO3
D. CuSO4

Answer

To determine which compound is alkaline in an aqueous medium, we will analyze the behavior of each compound when dissolved in water.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds we need to analyze are Na2CO3 (sodium carbonate), NaCl (sodium chloride), and CuSO4 (copper(II) sulfate).

2. **Dissolution of Na2CO3**:
- When Na2CO3 is dissolved in water, it dissociates into sodium ions (Na⁺) and carbonate ions (CO3²⁻).
- The carbonate ion can react with water to form bicarbonate (HCO3⁻) and hydroxide ions (OH⁻):
\[ CO3^{2-} + H2O \rightleftharpoons HCO3^{-} + OH^{-} \]
- The presence of hydroxide ions (OH⁻) indicates that the solution is basic (alkaline).

3. **Dissolution of NaCl**:
- When NaCl is dissolved in water, it dissociates into sodium ions (Na⁺) and chloride ions (Cl⁻).
- Neither ion reacts with water to produce hydroxide or hydrogen ions, so the solution remains neutral (pH = 7).

4. **Dissolution of CuSO4**:
- When CuSO4 is dissolved in water, it dissociates into copper ions (Cu²⁺) and sulfate ions (SO4²⁻).
- The copper ions can react with water to form copper hydroxide (Cu(OH)₂), but this is a weak base and does not significantly increase the pH. The overall solution remains slightly acidic due to the presence of the sulfate ion, which does not produce hydroxide ions.

5. **Conclusion**:
- Among the three compounds analyzed, Na2CO3 produces hydroxide ions and thus is alkaline in an aqueous medium. NaCl remains neutral, and CuSO4 is slightly acidic.

### Final Answer:
The compound that is alkaline in an aqueous medium is **Na2CO3 (sodium carbonate)**.